Expansible plunger



Feb. 15, 194-9 L. BEEH EXPANSI'BLE PLUNGER Filed April 11, 1946 INVENTOR.

147'7'0/9/VEY Patented Feb. 15, 1949 UNITED STATES ATENT OFFICE.

EXPANSIBLE PLUNGER Application April 11, 1946, Serial No. 661,281

Claims. 1

The invention relates to an expansible plunger, and the present application is a continuation in part of my co-pending application Serial No. M53126, filed July 18, 1944, on which Patent N0. 2,405,938 of August 20, 1946 has been granted and in which I have illustrated and described a plunger of the type here under consideration. In devices in which a reciprocating element, such as a plunger or piston, is subject to fluid pressure either in a driven or driving capacity, and where relatively minute quantities of fluid are to be dealt with, during each plunger stroke, it has been found extremely difficult to obtain the required exact fit between plunger or piston and the cylinder barrel in which the reciprocating element operates. Thus, e. g. in the mass production of fuel pumps of multi-cylinder engines, it frequently occurs that each plunger has to be separately fitted to the co-operating pump cylinder. In consequence, a damaged part cannot be readily exchanged or replaced, except by simultaneously exchanging or replacing also the co-operating part. These conditions not only slow down the production, but make the production unusually expensive.

The invention aims, therefore, to provide for the indicated purpose a plunger or piston which, within limits, can be readily adjusted to an exact fit in a cylinder barrel in which it is intended to reciprocate. The invention consists in a plunger or piston including a hollow tubular portion which is subject to interior pressure tending to expand or spread the tube walls against the barrel in which the plunger operates.

The hollow portion may be filled with a matter which will tend to spread and to bulge the tubular wall outward when compressed by an adjustable screw member closing the tubular portion, or the latter may be open and subject to the pump pressure during the operation, particularly during the compression stroke, of the plunger reciprocating in a pump barrel.

-ing to the invention.

Fig. 2 is a cross-section of a modified form, and

Fig. 3 is a cross-section of a third embodiment.

Referring to the drawing, the plunger, in gen eral denoted by I0, is shown in a. diagrammatically illustrated barrel H with an inletport i2 and screwedinto the tube.

an outlet port 13. The plunger may be reciprocated by any suitable and conventional means such as indicated by the cam-drive M in co-operation with a spring l5 interpositicned between the stationary barrel structure and the plunger. According to the invention, the body of plunger It) consists of a thin-walled tubular member l6 closed at its lower end by a plug I? which may be screwed into the tube as indicated at Hi. The plug is so shaped as to form a foot IQ for en gagement by.a driving means such as the mentioned cam M. The plug also forms a flange 2!! on which spring I5 bears in order to return the plunger for its suction stroke after the compression stroke has been completed under the action of the cam drive. If so desired, the tubular member [6 and plug I! may be made of one piece and designed similarly to the foot structure of the plunger shown in Fig. 3. It will also be understood that the plunger foot may be of any other design to suit the particular means by which the plunger is to be reciprocated, and that e. g. flange 20 is shown in the embodiment of Fig. 1' merely to accommodate spring 95. The upper end of the tubular member I5 is provided with an interior threading 2 l, into which another plug 22 is adjustably screwed. The interior of the tube [6 is filled with a material 23 which under pressure in one direction tends to spread in all other directions. Such matter may be either liquid or semi-liquid as a paste, or a highly ductile or elastic or granulated material. Even a gaseous filler may be used under suitable circumstances. Where the filler material is nonelastic, the elasticity of the plunger material will furnish that degree of resiliency that may be desirable in the device. Now, it will be. clear that if the plug 22 is tightened, the matter 23 will be compressed in axial direction and consequently tend to spread in radial direction. Thereby, an interior pressure is exerted on the thin wall of the tube which will bulge outwardly according to the depth to which plug 22 is Hence, by adjusting plug 22, i. e. by screwingv it more or less in or out with the aid of e. g. a screw driver engaging the slot 23, the bulge or active diameter of the plunger [0 can be adjusted within extremely narrow tolerances to fit the diameter of the barrel exactly. If the filler 23 is a highly elastic or ductile material such as rubber, indicated by the hatching in Fig. 1, I have found it advisable although not absolutely necessary, to add a conical pin 25 inserted from the top into the rubber in axial direction. The plug 22, then,

bearing on the head 26 of the pin will force the latter deeper into the rubber when the plug is tightened. The pin has the effect or directlycreating a radial pressure component to cause a bulge of the tube where desired.

In the embodiment of Fig. 2, the plunger body 30 comprises an upper, thin walled tubular portion 3| and a solid foot portion 32. No flange, such as flange 25in Fig. l, is shown but may be provided if so desired, or the foot may have any other form to suit the drive which may be applied. The tubular portion has a smooth cylindrical inner wall 33 throughout. Co-axial therewith and in continuation of the hollow plunger space, an interiorly screw threaded hole 34 extends downward a distance into the foot portion 32. A screw 35 having a head 35, a shaft 31 and a threaded end portion is screwed into the hole 34. Its shaft is of such a length that the head 35 at least partly engages in the top end of the tubular portion 3| when the threaded por tion 33 safely engages the threading of the hole 34 without however reaching the bottom of the latter. The head 36 has an outer diameter fitting the inner diameter of the tubular body portion 3|, and is so shaped that it may be engaged by a tool, e. g. a slot 39 for the application of a screw driver may be provided. A cup washer 40 is positioned underneath the screw head 35 so as to insure a tight closure of the plunger body to prevent the escape of material 41 which fills the space between the wall 33 and shaft 31 and is shown in the embodiment of Fig. 2 as a liquid; a heavy oil for instance being useful for the purpose of the invention. In order to secure the screw in an adjusted position whereby a desired expansion of the tubular portion 3! has been attained, a Securing pin 42 may be inserted in a bore 43 which extends through the foot portion 32 and the threaded screw portion 38.

This structure, shown in Fig. 2, ofiers the advantage over the first one described that it does not require an internal threading of the tubular body portion which for that reason can be pro vided with a thinner wall capable of bulging more readily under internal pressure.

In certain instances, it is desirable that the plunger fit in the barrel adjusts itself according to the pump pressure during the operation of the machine, so that the fit is tighter during the compression stroke and looser during the suction stroke of the plunger. A structure accomplishing such automatic change is shown in the embodiment of Fig. 3. In this figure, the plunger is reciprocatable in a barrel ll similar to that of Fig. 1. Also a similar drive comprising the cam l4 and spring 15 is.illustrated. Plunger 50, shown in its dead center position at the end of the compression stroke, is made of one piece comprising the foot portion 5| with the flange 52 serving as seat for the spring l5, and the thin-walled tubular portion 53 which is open on top. A piece 54 of a straight pipe having an outer diameter smaller than the inner diameter of plunger portion 53, is secured with its upper end to the material which constitutes the top closure of the barrel space, e. g. by a screw connection at 55. It extends co-axially downward into the portion 53 almost to the bottom of the latter, and it communicates at its top end with the barrel outlet opening [3. Now it will be clear, that regardless of what kind of fluid is pumped, the entire free plunger space 55, barrel space 51 and inner space 58 of pipe 54 will be filled with such fiuid when the plunger dur- 'IZ of the barrel.

ing the suction stroke opens the suction port If then, during the return stroke, the plunger operates against a back pressure created for instance by a conventional, loaded discharge valve (not shown) in connection with outlet t3, the pressure set up in space 56 will tend to spread the wall of the tubular portion 53 so as to tighten the fit between the plunger and the barrel the more the higher the inner pressure rises. As soon as the subsequent suction stroke begins, the tight fit will be eased owing to the resiliency of the plunger material. In consequence the danger of the plunger freezing in the barrel is greatly reduced. This structure where applicable, offers also the advantage of great simplicity.

It will be noticed that in the operation of the plunger of Fig. 3, the inner pressure will act on the wall of the tubular portion 53 during the compression stroke, regardless whether or not the fixed pipe 53 is provided. In fact, this pipe may be omitted. Its actual purpose is merely to prevent the formation of air pockets when a readily evaporating fluid is pumped, because air or vapor which otherwise may accumulate in the plunger can be carried away by the fluid passing through the pipe.

Although in the foregoing, I have referred mainly to pump plungers, it will be clear that the described devices may also be used as pistons of reciprocating engines; furthermore, it will be apparent to those skilled in the art that many alterations and modifications of the embodiments illustrated by way of example are possible without departure from the essence and spirit of my invention, which therefore, shall not be limited but by the scope of the appended claims.

Iclaim:

1. A plunger or piston of the character described comprising a thin-walled tubular portion forming an axially extending chamber closed at one of its ends, a filler within said chamber, said filler being of a material which when subjected to pressure in one direction tends to spread readily in the other directions, and means in engagement with said tubular portion and adjustable as to its distance from said closed cham ber end to close the other chamber end and to exert adjustable pressure on said filler.

2. A plunger or piston of the character described comprising a body including a foot portion for co-operation with a reciprocating drive, and a thin-walled tubular portion in co-axial continuation of said foot portion, a filler within said tubular portion, said filler being of a material which when subjected to pressure in one direction tends to spread readily in other directions, and means in engagement with said body, to close said tubular portion at its top and to exert adjustable pressure on said filler.

3. A device as claimed in claim 1, said filler having elastic properties similar to rubber.

4. A device as claimed in claim 1, said filler being a liquid, completely filling the space of said chamber when the latter is closed.

5. A device as claimed in claim 1, said filler being a granulated material, completely filling the space of said chamber when the latter is closed. I

6. A plunger or piston comprising a body including a foot portion adapted for co-operation with a reciprocating drive and a thin-walled tubular portion in co-axial continuation with said foot portion, a filler within said tubular portion, said filler being of a. material which when subjected to pressure in one direction tends to spread readily in other directions, a screw member in engagement with a threading of said body, said screw member closing said tubular member at its top and being adapted to exercise adjustable pressure on said filler.

7. A device as claimed in claim 6, said tubular body portion being interiorly threaded in its top end, and said screw member being a plug screwed into said threading.

8. A device as claimed in claim 6, said filler being of a rubber-like material, a conical pin being inserted from the top of the tubular portion into said filler, and said screw member being a plug screwed into the top of said tubular portion so as to close the latter and to bear with adjustable pressure on said pin.

9. A device as claimed in claim 6, said threading of said body being provided in said foot portion so as to extend co-axially with said tubular portion a distance downward from the lower end thereof, said screw member including a head, and a screw threaded end, said head fitting into REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,340,596 Boulade Ma 18, 1920 1,384,401 Noble July 12, 1921 1,517,777 Flint Dec. 2, 1924 1,531,234 Davis Mar. 24, 1925 1,678,957 Philipp July 31, 1928 1,876,917 Gosslau Sept. 13, 1932 1,945,524 Foehr Feb. 6, 1934 

